Three Redshifts: Doppler, Cosmological, and Gravitational

Abstract

The concept of redshift is very often used in teaching physics and astronomy, as well as in science public outreach. Redshift is an interesting topic, used to describe many physical processes such as the Doppler effect or the expansion of the universe. Nevertheless, there are unfortunately also misconceptions about redshift. When facing the redshift topic with students and teachers, we have to focus sometimes on dissolving these misconceptions. Therefore, the idea of this paper, in which the most common misconceptions are treated, arose from direct experience and discussions with colleagues in the field. This article explains what redshift is and how it works. Moreover, since redshift has a great potential for teaching and is usable in many physics and astronomy problems, examples and specifically developed exercises are also used in this article.